Fluorinated carbon is known by the formula (CF.sub.x).sub.n, where x is a number between 0 and 1.5 and n is an indefinite number greater than 2. Hereafter, (CF.sub.x).sub.n is abbreviated as CF.sub.x. Fluorinated carbon is ordinarily obtained by fluorinating a crystalline or amorphous carbon with elemental fluorine gas at elevated temperature. One of the major applications of the fluorinated carbon is a cathode active material in a lithium, i.e., Li/CF.sub.x, battery. This Li/CF.sub.x battery shows many advantages over other types of lithium batteries. The advantages include high energy density, flat discharge curve and long shelf life., etc. However, there is a characteristic voltage delay at the initial discharge stage. This voltage delay adversely impacts its applications.
Numerous disclosures have been made in the prior art with the aim of proving the initial discharge voltage of the lithium/fluorinated carbon batteries. Some of these prior art efforts to eliminate or reduce initial voltage suppression are summarized as follows:
The following Japanese unexained patent applications disclose the addition of a fluorinated carboneous materials to the CF.sub.x to reduce or elminate the initial voltage delay.
Japanese Kokai No. 83 05,967 discloses the addition of a fluorinated carbon black made from a starting carbon black having a specific surface area of 800 m.sup.2 /g;
Japanese Kokai No. 82 84,570 discloses the use of a mixture of 10 to 50 wt. % of polydicarbon monofluoride, (C.sub.2 F).sub.n, and the CF.sub.x to elminate the initial voltage delay;
Japanese Kokai No. 84 31,564 discloses the use of carbon containing adsorbed fluorine in the CF.sub.x electrode to replace the carbons which are typically used to provide the electrical conductivity of the electrode matrix; and
Japanese Kokai No. 82 206,057 discloses the incorporation of a AlF.sub.3 or MgF.sub.2 and F2 intercalated graphite fluoride ternary compound into a CF.sub.x cathode to improve the initial discharge voltage.
The following Japanese patent publications disclose the use of a variety of materials which do not contain fluorine and are indicated as having the capability to elminate or reduce the severity of voltage suppression in Li/CF.sub.x cells;
Japanese Kokai No. 83 123,663 discloses the addition of aluminum powder;
Japanese Kokai No. 83 206,058 discloses the addition of aluminum fiber to CF.sub.x cathode compositions for the purporse of stabilizing the initial discharge voltage; and
Japanese Kokai No. 83 161,260 disclosed the addition of compounds of the form Cr.sub.x O.sub.y where 15&lt;y/x &lt;3. Examples given are Cr.sub.3 O.sub.6 and Cr.sub.2 O.sub.5. These additives are claimed to improve the initial drop in cell voltage.
The following references disclose miscellaneous efforts to alter the discharge voltage such as by chemical pretreatment, electrochemical predischarge, etc.
Japanese Kokai No. 84 87,762 discloses defluorination of over-fluorinated CF.sub.x by using aqueous HI solution in the presence of methanol can improve the initial discharge characteristics;
Japanese Kokai No. 84 86,155 discloses the UV irradiation of CF.sub.x in the NaOH/MeOH solution to reduce the initial voltage delay;
Japanese Kokai No. 77 10,519 discloses the use of a CF.sub.x with high free oxidizing power, which has a deleterious effect on the shelf life of the Li/CF.sub.x battery;
Japanese Kokai No. 83 140,972 discloses the use of a fluorinated carbon obtained from fluorinating a mixture of graphite or petroleum coke with a cabon black having a surface area .gtoreq.800 m.sup.2 /g;
Japanese Kokai No. 80 31,991 discloses the use of a CF.sub.x obtained by subsequent refluorination of a pulverized CF.sub.x of large particle size (200 mesh) for the purposes of improving the initial discharge characteristics; and
Japanese Kokai No. 82 124,865 discloses that Li/CF.sub.x batteries can be partially discharged to less than 10% of the battery capacity to improve the initial discharge voltage. This practice minimizes the voltage delay but suffers from several disadvantages; an additional step is required in the production process, processing time is increased, and additional equipment is required.
Each of the foregoing approaches suffers from one or more disadvantages from the standpoint of, for example, economy, practicality and complexity. Therefore, a need exists for a process to prepare a fluorinated carbon with no initial voltage delay upon discharge in a Li/CF.sub.x battery and free of the aforementioned draw-backs of free oxidizing power.